Supremely obvious observation: We love the Web. We love scrolling through tweets and blog posts and constantly updated news sites like rats in Skinner boxes. We love accessing the cloud, floating up into that sweet mass of data like Icarus and his wings of wax and feather.

The mere sound of our iPhone's chirp activates the brain regions involved in love and compassion, research shows. The bond we share with our computers or smartphones is, for many of us, the most lasting and fulfilling relationship we've managed to hold on to.

But when it comes to our gadgets, absence doesn't make the heart grow fonder. If you find yourself unhooked from your digital life support (say, because your phone is dead, your laptop is in the shop or you're wrapping up last week's challenge to put the phone down and look around this lovely world), you may need to ask those five little words: "Can I use your computer?"

Sitting down at the keyboard of another requires a delicate mix of courtesy and discretion. Beyond the insanely obvious (DON'T invade your friend's privacy by opening his files or checking his e-mails, DON'T watch porn or download malware or Google anything that will get the attention of the Department of Homeland Security, and so on), there are a few more subtle guidelines to keep in mind while bumming a friend's computer or tablet.

Read on to be a polite MacBook mooch. (Oh, and if you're the auntie letting your nieces and nephews use your MacBook when the littl'uns complain of boredom, this just may help you set some ground rules before you hand over the machinery.)

DON'T assume the owner wants to give you his/her password.

Three out of four people use the same password to access multiple sites, a study from Internet security company BitDefender shows. So by saying the security code aloud, you just might be demanding your friend's banking, e-mail and insurance sign-on.

Plus, the password might be something embarrassing (think "windbeneathmywings"). Say, "Oh, looks like it needs your password!" and casually get out of the way of the keyboard.

DO ask before altering the hard drive.

Obvious, but worth stating: Don't download any plug-ins, run any new programs, etc. on someone else's computer. If your bud doesn't have Adobe Reader, this isn't your night to access that fancy PDF.

Equally important: Unless you've cleared it, don't download e-mail attachments. They can easily get buried in labyrinthine folders, invasive for you to dig out before signing off but cluttering up your bud's files.

DON'T leave a trail of cookie crumbs.

It's annoying to use your computer after a friend's been on it and see that when you visit your Facebook, e-mail, Tumblr and Pinterest, you're already logged in as said user.

Don't be that borrower; instead, turn off cookies so that whatever you're doing isn't remembered for all time by the friend's browser (although, as NPR pointed out last week, the programs are far from foolproof should someone really want to see what you were doing online.).

Different browsers call this amnesiac mode different things: In Internet Explore, it's InPrivate Browsing; in Chrome, it's Incognito Mode; in Firefox, it's Private Browsing. Just remember to turn it off when you're done. If nothing else, it'll prevent your judgy friend from seeing that you had to Google "when to use lay and lie." And on a related note ...

DO withhold judgment.

We all search for embarrassing things, things that, thanks to the wonder of personal computers, our beloved gadgets remember for all time.

Whether a browser history reveals that your friend has been checking what SOPA means or just checking up on an ex, you must never use the information against her.

She's doing you a favor, after all. She's giving you another sweet hit of e- before you start to get the shakes.